WELL AP key terms

Airborne particles with a diameter of 2.5 micrometers or less. They travel deep into the lungs and bloodstream and are linked to heart and lung disease, so WELL sets indoor concentration limits and filtration requirements.

The combined concentration of volatile organic compounds measured in indoor air, including fumes from paints, adhesives, cleaners and furnishings. It is a broad indicator of chemical pollution that WELL limits through product and ventilation requirements.

Minimum Efficiency Reporting Value: a 1-to-16 scale describing how effectively an air filter captures particles of different sizes. WELL requires filters rated at least MERV 13 in mechanically ventilated spaces.

Using sensors to track indoor CO2, which rises as occupants exhale in poorly ventilated rooms. WELL rewards real-time displays and demand-controlled ventilation because the readings show whether fresh air is adequate.

A measure of how cloudy water is because of suspended particles. High turbidity can hide microbes from disinfectants and signal contamination, so WELL sets a maximum level for drinking water.

A toxic heavy metal that can leach into drinking water from old pipes, solder and fixtures. Even low exposure harms children's brain development, so WELL requires testing and treatment where lead is a risk.

The combined concentration of minerals, salts and metals dissolved in water. It affects taste and can hint at contamination, and WELL caps the level allowed in drinking water.

Bacteria that multiply in warm, stagnant water systems such as cooling towers and hot-water tanks, causing Legionnaires' disease. WELL requires a management plan to control their growth.

Sugars introduced to food or drink during processing, as in sodas, baked goods and sweetened yogurts, beyond what occurs naturally. WELL limits added sugar in foods sold or provided in the building.

Making nutrition information such as calories, sodium, sugar, saturated fat and ingredients readily visible for foods offered in a building, so occupants can compare options and make informed choices.

Clearly identifying major food allergens - such as peanuts, tree nuts, milk, eggs, shellfish, wheat and soy - in foods served or sold, so people with allergies can avoid dangerous exposures.

Limits on promoting unhealthy foods such as sugary drinks, candy and fried snacks through signage, displays or vending placement inside a building, so the cues occupants see favor healthier options.

A metric that weights light according to how strongly it stimulates melanopsin in the eye's light-sensitive ganglion cells. It expresses a light source's circadian impact in lux-like units, letting designers compare daytime alerting potential.

Designing electric lighting and daylight so occupants get bright, blue-enriched light during the day and dimmer, warmer light in the evening, supporting the body's natural sleep-wake rhythm.

Brightness in the field of view far greater than the eyes are adapted to, causing squinting, discomfort or temporary loss of vision. It is controlled with shading, baffles and luminance limits.

The percentage of regularly occupied floor area that reaches a target daylight level, typically 300 lux, for at least half of the occupied hours in a year without electric lighting.

Any bodily movement that raises energy use above resting, such as walking, stair climbing or exercise. WELL encourages it through building design, programs and policies rather than relying on individual willpower.

An approach that shapes buildings, streets and programs so movement becomes the easy default - visible stairs, bike parking, walkable paths - rather than a chore requiring extra effort.

Long periods of sitting or lying down with very low energy expenditure. WELL addresses it with reminders to move, standing-capable workstations and policies that break up prolonged sitting.

A comfort model that predicts the average thermal sensation of a large group on a scale from minus 3 (cold) to plus 3 (hot), based on air temperature, radiant temperature, humidity, air speed, clothing and activity.

The share of occupants a comfort model predicts will feel too warm or too cool at a given Predicted Mean Vote. WELL aims for a low value, accepting that no single condition suits everyone.

A difference in radiant temperature between surfaces on opposite sides of a person, such as a cold window on one side and a warm wall on the other, which causes local discomfort even when air temperature is fine.

The ability of occupants to adjust conditions themselves by changing setpoints, using a fan, opening a window or moving to another zone, because comfort preferences vary widely between people.

A logarithmic measure of sound intensity expressed in decibels. A-weighted values (dBA) approximate how loud a sound seems to human hearing, and WELL sets limits for background noise.

The time it takes for sound to fade by 60 decibels after its source stops. Long reverberation makes speech echo and hard to understand, so WELL sets targets by room type.

Adding a low, unobtrusive broadband background sound to a space so nearby conversations become less intelligible and less distracting, without raising overall noise to annoying levels.

Publicly disclosing what a building product contains and the health hazards linked to those ingredients, so specifiers can choose safer materials instead of guessing about chemical content.

A standardized, third-party-verified report listing a product's contents and the health hazards associated with each ingredient. It helps project teams compare materials and meet WELL disclosure requirements.

A roster of worst-in-class chemicals and materials, such as certain flame retardants, phthalates and heavy metals, that WELL and other green building programs discourage or prohibit in building products.

The greenhouse gases released while extracting, manufacturing, transporting, installing and disposing of building materials. It is quantified by life cycle assessment and is separate from operating energy use.

The amount of volatile organic compounds in a product such as paint, adhesive or sealant, often given in grams per liter. Lower content means less chemical off-gassing once the product is installed.

Designing buildings to include nature and natural patterns - plants, daylight, views, wood, water and varied textures - because these elements measurably reduce stress and improve mood and attention.

A quiet, comfortable area set aside for rest, contemplation or recovery during the day, giving occupants a break from noise, crowding and constant demands on attention.

Features and policies that protect sleep, such as limiting bright or blue-rich light in the evening, providing quiet rest areas, and offering schedules or education that discourage chronic sleep loss.

Written rules covering tobacco, vaping, alcohol and other substances, including smoke-free grounds and support for quitting, that reduce exposure and encourage healthier behavior among occupants.

A structured questionnaire collecting occupants' perceptions of comfort, health and satisfaction with the building. WELL requires repeated surveys and expects results to guide concrete improvements.

A written, owner-approved commitment describing how the building will be operated to support occupant health - cleaning, smoking, food, exercise and similar topics - with regular review and updates.

Designing spaces, fittings and information so people of all ages and abilities can use them without special adaptation, through step-free routes, reachable controls and clear signage.

Planning and equipment for health emergencies, such as first aid supplies, AEDs, trained responders and clear procedures, so occupants can act quickly when someone is injured or suddenly ill.